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maximum charging rates be used. Assuming that the maximum is 3 amperes, to pass a current of this value through the battery, it will be necessary to screw in 6-16 candle power lamps which will average 55 watts each, which means that at a pressure of 110 volts they require a current strength of half ampere. If fitted with 16 candle power lamps the 12 socket lamp bank will pass 6 amperes, and double this amount with lamps of twice the candle power.

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Fig. 79.–Lamp Bank Resistance for Charging a Number of Storage

Batteries Simultaneously.

The meter installation shown between the charging boards is to determine the amount of current passing through the storage battery and as it is a low reading instrument, a low resistance shunt is interposed so that any overload will pass over the shunt instead of through the instrument which is calibrated to measure currents up to 30 amperes. With the small single blade knife switches in circuit the current will not pass through the instrument, as it is not advisable to include this in the circuit permanently, because the passage of current through the windings may result in injurious heating. To get a reading from either side the single blade

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switch is thrown off and the double throw male member of switch is placed in contact between the blades on the side of which a reading is to be taken. It will be seen that the

Cell Cover wires are crossed at

Apperture the right of the two Pole v e way switch to cause the current to flow through the instru

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Negative Flo Level rection and also to

Positive have the negative terminal of each charging

Negative 1 board at the left. This eliminates any confusion and the terminals are plainly marked so it is not possible to make a mistake when coupling batteries. When more than one battery or set of cells is being charged they are wired in series, the negative terminal of one battery being coupled to the positive terminal of the neighboring one. In con

Fig. 80.—Sectional View of Edison necting a battery to

Alkaline Storage Battery Cell. the charging board the negative wire should always be coupled to the negative terminal of the battery and the positive wire to the corresponding battery terminal.

Features of the Edison Cell.—The instructions given apply only to batteries of the lead plate type and not to the Edison bat

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tery, which is entirely different in construction. The Edison cell, shown in section at Fig. 80, uses an electrolyte consisting of 21% solution of potash in distilled water so that the electrolyte is alkaline instead of acidulous. The positive plates consist of a series of perforated steel tubes which are heavily nickel-plated and which are filled with alternate layers of nickel hydroxide and pure metallic nickel in very thin plates. The tube is drawn from a perforated ribbon of steel, nickel-plated and has a spiral lapped seam. After being filled with active material it is reënforced with eight steel bands which prevent the tube expanding away from and breaking contact with its contents. The negative plate consists of a grid of cold rolled steel, also heavily nickel-plated, holding a number of rectangular pockets filled with powdered iron oxide. These pockets are also made up of finely perforated steel, nickelplated. After the pockets are filled they are inserted in the grid and subjected to considerable pressure between dies which corrugate the surfaces of the pockets and forces them into positive contact with the grids. These elements are housed in a jar or container made from cold rolled steel which is thoroughly welded at the seams and heavily nickel-plated. The plates are assembled in positive and negative groups by means of threaded steel rods passing through holes in one corner of the plates and insulating washers. The terminal post is secured to the middle of the rod. The complete element or plate assembly stands on hard rubber bridges on the bottom of the can as at Fig. 81 and is kept out of contact with the sides of the container by hard rubber spacers attached to the end. The can cover is also of sheet steel and contains fittings through which the electrodes pass, these being insulated from the cover by bushings of insulating material. A combined filling aperture and vent plug is secured to the center of the cover plate. For 6 volt ignition and lighting service it is necessary to use 5 cells owing to the lesser voltage of the Edison batteries. The average voltage during discharge is but 1.2 volts per cell and is not as constant as is the case with a lead battery, the voltage of which may be as high as 2.5 volts per cell.

An Edison 6.5 volt battery (Fig. 81) used for lighting or ignition may be charged completely in ten hours. A feature of the

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Fig. 81.–Plate Construction of Edison Cell and Method of Grouping

Cells to Form Lighting or Ignition Battery.

Edison battery is that overcharging at the normal rate has no harmful effects and it is advised by the maker to give the battery a 12 hour charge once every 60 days or when the electrolyte is replenished. The electrolyte must be kept sufficiently high so as to cover the plates and any loss by evaporation must be compensated for by the addition of distilled water. Another feature in which the Edison battery is superior to the lead plate type is that the plates will not be injured if the cells are allowed to stand in a discharged condition. The external portions of the cells must be kept clean and dry because the container or can is made of a conducting material. The vent caps must be kept closed except when replacing electrolyte or bringing the level up to the proper height by adding distilled water. Care should be taken to avoid short circuiting of the battery by tools or metal objects and special emphasis is laid on the precaution that no acid or electrolyte containing acid be poured into the cells. It is said that the Edison battery has a longer life than the lead plate type of equal capacity. While eminently suited for ignition and lighting, also for vehicle work, it is not as well adapted for starting purposes as the lead plate battery is.

Winter Care of Storage Batteries.-It would not do simply to leave the battery in the car for a period of, say, 4 or 5 months without giving it any care or attention, for in that case at the end of that time it would be found to have its plates so thickly covered with lead sulphate as to make it practically useless. For storage batteries “to rest is to rust” and become ruined, unless special precautions are taken. Automobile storage batteries are all or nearly all of the sealed-in type from which the elements cannot be removed without a great deal of trouble. Therefore, the only method of keeping the plates intact consists in charging the battery at intervals of about two weeks. The following advice concerning the care of batteries during a protracted period of idleness of the car is due to the Willard Storage Battery Co., and refers especially to the batteries of starting and lighting systems.

At intervals of 2 weeks the engine should be run until the electrolyte shows a specific gravity of 1.280. If this is done regu

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